Primary or isolated chylopericardium of unknown etiology is considered a rare cause of pericardial effusion. Its etiology is obscure but certain communication between the lymphatic system and pericardial sac was suggested. Up to 1991, there was only one case report that successfully showed the direct communication by a lymphangiogram. We report a case of chylopericardium occurring in a nearly asymptomatic 22-year-old man with no apparent history of trauma, infection or mediastinal neoplasm, in which we succeeded in visualizing the communication between the thoracic duct and pericardial sac by lymphangiography and computed tomography of the chest. A review of the previous cases is described also.